Use openid-configuration file for OIDC login setup
Add a button in the OIDC login setup to read the openid-configuration metadata endpoint.
ArcGIS Enterprise Portal supports OpenIDConnect (OIDC) login from an upstream identity provider; this is a modern standard which is replacing the older SAML authentication.
In the configuration documentation (https://enterprise.arcgis.com/en/portal/latest/administer/windows/openid-connect-logins.htm), it suggests that the user should open the [server]/.well-known/openid-configuration JSON file and extract 6 values from it and put them into the login configuration fields. This should be automated by having the form pull values from that configuration file directly. The openid-configuration JSON follows a standard (https://openid.net/specs/openid-connect-discovery-1_0.html#ProviderMetadata) designed precisely for this use case, where an application needs to be configured to work with an upstream identity provider.
By adding an input for the openid-configuration endpoint and a button to pull that data, 6 fields could be auto-populated: Provider issuer ID, OAuth 2.0 authorization URL, Token URL, JWKS URL, User profile URL, and Logout URL. Having this automated would simplify the setup experience for the user and reduce the potential for errors.
